Mechanisms of Synergistic Removal of Low Concentration As(V) by nZVI@Mg(OH)<sub>2</sub> Nanocomposite

Abstract

In this work, by using Mg­(OH)<sub>2</sub> nanoplatelets as support material for nanoscale zerovalent iron (nZVI), nZVI@Mg­(OH)<sub>2</sub> composite was prepared and found to have super high adsorption ability toward As­(V) at environmentally relevant concentrations. It was revealed that the variation of corrosion products of nZVI in the presence of Mg­(OH)<sub>2</sub> and Mg<sup>2+</sup> is an important factor for increase in the adsorption ability toward As­(V). X-ray diffraction (XRD) analysis indicated that the weakly basic condition induced by Mg­(OH)<sub>2</sub> decreases the lepidocrocite (γ-FeOOH) and increases the magnetite/maghemite (Fe<sub>3</sub>O<sub>4</sub>/γ-Fe<sub>2</sub>O<sub>3</sub>) content in the corrosion products of nZVI, and the latter has better adsorption affinity to As­(V). Moreover, extended X-ray absorption fine structure spectroscopy (EXAFS) indicated that the coordination between arsenic and iron minerals is influenced by dissolved Mg<sup>2+</sup>, leading to probable formation of magnesium ferrite (MgFe<sub>2</sub>O<sub>4</sub>) which has considerable adsorption affinity to As­(V). This work provides an important reference not only for the design of pollution control materials but also for understanding arsenic immobilization in natural environments with ubiquitous Mg<sup>2+</sup> ion

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